In recent years, there have been dramatic improvements in LED technology such that LEDs of increased brightness and color fidelity have been introduced. Due to these improved LEDs and improved image processing technology, large format, full color LED video screens have become available and are now in common use. Large format LED displays typically comprise a combination of individual LED panels providing image resolutions determined by the distance between adjacent pixels or “pixel pitch.”
Outdoor displays, which are intended for viewing from greater distances, have relatively large pixel pitches and usually comprise discrete LED arrays. In the discrete LED arrays, a cluster of individually mounted red, green, and blue LEDs are driven to form what appears to the viewer as a full color pixel. Large screen LED based displays (often referred to as giant screens) are becoming more common in many indoor and outdoor locations, such as at sporting events, race tracks, concerts and in large public areas such as Times Square in New York City. Many of these displays or screens can be as large as 60 feet tall and 60 feet wide. These screens can comprise thousands of “pixels” or “pixel modules”, each of which can contain a plurality of LEDs. The pixel modules use high efficiency and high brightness LEDs that allow the displays to be visible from relatively far away, even in the daytime when subject to sunlight. The pixel modules can have as few as three or four LEDs (one red, one green, and one blue) that allow the pixel to emit many different colors of light from combinations of red, green and/or blue light. In the largest jumbo screens, each pixel module can have dozens of LEDs. The pixel modules are arranged in a rectangular grid. For example, a grid can be 640 modules wide and 480 modules high, with the end size of the screen being dependent upon the actual size of the pixel modules.
Conventional LED based displays are controlled by a computer system that accepts an incoming signal (for example a TV signal) and based on the particular color needed at the pixel module to form the overall display image, the computer system determines which LED in each of the pixel modules is to emit light and how brightly. A power system can also be included that provides power to each of the pixel modules and the power to each of the LEDs can be modulated so that it emits at the desired brightness. Conductors are provided to apply the appropriate power signal to each of the LEDs in the pixel modules.
Most of these giant screens are typically mounted at an elevation above the viewer's eye level, such as on the side of building or the top of the grandstands in a stadium. Accordingly, much of the light emitted by the display is not seen by the viewer and is wasted. Additionally, the wasted light may cause light pollution by creating unwanted light reflection and/or glare. One way to reduce the amount of light that is wasted is by mounting the display at an angle to better match the viewer's line of sight, but this can require complex and expensive mounting hardware that is difficult to use, particularly for very large displays mounted at high elevations.